/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.rpc.service;

/**
 * Echo service.
 * 回声测试用于检测服务是否可用，回声测试按照正常请求流程执行，能够测试整个调用是否通畅，可用于监控
 *
 * 配置：
 * <dubbo:reference id="memberService" interface="com.xxx.MemberService" />
 * 代码：
 * // 远程服务引用
 * MemberService memberService = ctx.getBean("memberService");
 *
 * EchoService echoService = (EchoService) memberService; // 强制转型为EchoService
 *
 * // 回声测试可用性
 * String status = echoService.$echo("OK");
 *
 * assert(status.equals("OK"));
 *
 *
 * 服务提供者，是不实现 EchoService 接口，而是通过 EchoFilter 实现
 *
 * @export
 */
public interface EchoService {

    /**
     * echo test.
     *
     * @param message message.
     * @return message.
     */
    Object $echo(Object message);

}